In light of the recent release of the "Underground PHP and Oracle Manual" from the folks over at Oracle, Dan Scott has posted his own note about a pet project of his along the same lines - official task-oriented documentation for the pairing of DB2 and PHP.
By "task-oriented" I mean that, instead of documenting a set of objects and methods, the docs take the perspective of a developer and describe how to accomplish specific tasks (like "Connecting to a DB2 database from PDO" or "Calling a stored procedure" or "Retrieving multiple result sets"). I hope it works as both a good introduction to PHP development for DB2 users, and a good introduction to DB2 for PHP developers. And, of course, the same approach will work for Apache Derby databases as well.
He notes that he also finds it interesting that the Oracle folks went with the "underground" method of documenting its relationship to PHP, while the IBM documentation is integrated right in.